Round Robin is always peeking the largest weight even using random node id

[jizhuozhi]

When the node with the largest weight is unique, no matter how the initial last_id is selected, the first peeked node will always be the node with the largest weight, which will cause this node to overheat.

For example, we have nodes with weights 5, 1, 1, 1, 1, the distribution is always

1
1
1
1
1
2
3
4
5

because when cw = max_weight, only the node with the largest weight satisfies condition weight >= cw